In similar bearings lubricated with grease, it is important that the grease captured in the second space, after flowing through the supporting elements and therefore having completed its greasing action and now constituting used lubricant, be inspected on a regular basis because the condition of this used grease reveals the condition of the bearing. Any developing defect in the bearing may thus be detected at an early stage.
For this purpose, in known bearings, the cover of the second opening is removed according to a regular schedule and, by means of some tool, a sample of the grease is taken from the second space and examined. However, sampling the grease in this manner is a complicated operation and, although the schedule may be written down, e.g., on a card specifically intended for the bearing, people often forget to take grease samples at the proper time.